Filament for incandescent electric lamps



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A; P. OPPERMANN. FILAMENT FOR INGANDESGENT ELECTRIC LAMPS.

No. 408,740. Patented Aug. 13, 1889.

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UNITED STATES PATENT OFFICE.

ADOLF F. OPPERMANNQOF CHICAGO, ILLINOIS.

FILAMENT FOR INC ANDESCENT ELECTRIC LAMPS.

SPECIFICATION forming part of Letters Patent N0. 408,740, dated August13, 1889.

' Application filed April 11, 1889. Serial No. 306,848. (No model.)

.To all whom it may concern:

Be it known that I, ADOLF F. OPPERMANN, a subject of the Queen of GreatBritain, residing at Chicago, in the county of Cook and StateofIllinois, have invented a certain new and useful Improvement inIncandescent Electric Lamps, of which the following is a full, clear,concise, and exact description, reference being had to the accompanyingdrawings, forming a part of this specification.

My invention relates to the manufacture of incandescent lamps, and more,especially to the filament; and its objects are, first, to increase thelife of the filament; second, to prevent its becoming warped or bent,and, third, to secure a battery-connection between the leading-in wiresand the ends of the filament. Heretofore the filament has been made fromdifferent kinds of vegetable fiberstrips of paper, cotton yarn; bamboo,and grasses of different varieties having been used in theirmanufacture. The filaments, after being carbonized, have been subjectedto an electric current While surrounded by hydrocarbon gas. and heated,is re-enforced by a coating of carbon taken up from the gas. When cottonyarn has been used, the filaments often be come distorted, owing to thetendency of the fiber to untwist, even after being carbonized. Cementsof various kinds have been used for mounting the filaments upon the endsof the platinum wires leading in through the globe. India-ink mixed withstove-polish has sometimes been used for this purpose;

My invention consists in subjecting the cotton thread to a high degreeof pressure, so as to-crush the fiber before it is carbonized, so as toavoid the distortion of the filament, heretofore resulting from thetendency of the fiber to untwist.

My invention consists, also, in subjecting the carbonized filament tothe action of an alternating current while the filament is surrounded byhydrocarbon gas, so as to make the coating or deposit thickest at theupper portion or curve of the filament.

I preferably make use of a mixture of ill.- dia-ink and platinum-blackas a cement for mounting the filament upon the leading-in wires, thiscement having been found by me The filament, being thus surroundedcoating than the legs 0.

more satisfactory than other cements now in use.

My invention is illustrated in the accompanying drawings, in whichFigure 1 is a side elevation of a machine adapted to crush the fiberofthe cotton yarn. Fig. 2 is a side elevation of a lamp provided with afilament embodying my invention. Figs. 3 and 4 are detail views of thefilament. Fig. 5 is a sectional view of a tank containing gasoline andilluminatinggas, a filament being inserted therein for the pur pose ofreceiving the carbon coating.

Referring now to Fig. 1, the rollers a should be smooth and fittedclosely together, like jewelers rolls used for flattening sheet metal.The end of the cotton yard or thread is placed between these rolls, andthe crank being turned the thread is drawn through and compressed tosuch an extent as to prevent any tendency of the fiber to untwist. Thethread being thus compressed, I next cut it into the lengths required,after which the separate pieces are carbonized. The next step in themanufacture is to coat these filaments with a deposit derived from thehydrocarbon, this coating being made thicker at the curved or upperportion of each filament. In order that such increased thickness may beobtained, I send current in alternations through each filament whilesurrounded by the hydrocarbon. I also preferably place the curvedportion in an atmosphere of denser gas than that which surrounds thelegs of the filament. Thus, as shown more clearly in Figs. 2 and 3, thecurved portion 1) of the filament has received athicker This is causedby the alternating current heating the curved portion to a greaterextent than the legs or sides are heated, and also on account ofsubjecting the curved portion to a denser atmosphere of as. b Thefilament is secured to the platinum leading-in wires (1 by cement 6,consisting of a mixture of india-ink and platinum-black, a smallproportion of the platinum-black being sufficient. I preferably use onepart of platinum-black to twenty parts of india-ink.

The preferable manner of coating the filament is illustrated in Fig. 5.A vessel f containing gasoline of suflicient depth to cover the filamentwhen inserted therein is surrounded by the gas-chamber g, a smallopening being provided, preferably in the top of the gas-chamber,through which the filament may be inserted. The holder his provided withclamps i, and the ends of the filament are held, as shown, by theseclamps. The holder contains wires connected with a suitable source ofalternating current, these wires being connected with the metal springsof the clamps, so that when the filament is inserted therein saidfil'ament will be included in the circuit over which the current isbeing sent in alternations. This current should be of sufiieientstrength to heat the filament to incandeseence, and, as is wellunderstood, the upper or central portion of the filament will be heatedmore than the sides.

The filaments are placed upon the holder one after another, each beingsubjected to the action of the alternating current while immersed in thegasoline and, preferably, for a short time-say four or fiveseconds-while the curved portion is above the surface of the gasolineand surrounded by the dense hydro carbon gas, while the legs or sidesare covered by the gasoline. The upper portion, which is surrounded bythe gas under these conditions, will be heated to a much highertemperature than the portion Which is immersed in the gasoline. Ipreferably use at the same time the alternating current and alsosuitable means for bringing the gas against the upper portion only ofthe filament. A continuous current would cause a thicker deposit uponthe curved portion if the gas about said portion were more dense thanabout the sides of the filament; but the same eifeet would be producedif the gas were entirely prevented from coming in contact with the sideswhile the upper portion was surrounded. The alternating current,however, in itself causes a thicker deposit at the curved portion of thefilament-that is to say, at the central portion of the resistancethereof, though the gas surrounding the entire filament should be of thesame density.

Lamps provided with filaments which have received a thicker coating atthe upper or curved portion thereof, as hereinbefore described, andwhich are secured to the leadingin wires by a cement of india-ink andplatinum-black are more durable, especially in alternating systems, thanany lamps heretofore in use, the tendency of the filament to break atthe central portion of its resistance being compensated for and overcomeby the greater thickness of the coating.

Having thus described my invention, I claim as new and desire to secureby Letters Patent 1. The method of manufacturing filaments forincandescent lamps, which consists in crushing the twisted fiber of thefilament, carbonizing the same, and then subjecting the filament thuscarbonized to the action of an alternating current while surrounded byhydrocarbon gas, substantially as and for the purpose specified.

2. The process of manufacturing filaments for incandescent lamps, whichconsists in crushing the twisted fiber before it is carbonized, thencarbonizing the filament and subjecting the same to an alternatingcurrent While surrounded by hydrocarbon gas, the gas being denser at theupper or curved portion of the filament, substantially as and for thepurpose specified.

3. In the manufacture of a filament for an incandescent lamp, theprocess eonsistingof subjecting the carbonized filament to the action ofan alternating current while surrounded byhydroearbon gas, the exposureto the hydrocarbon gas at the curved portion thereof or central portionof the resistance thereof being continued for a greater time than theexposure of the other portions thereof, whereby the coating is madethicker at the said central or curved portion thereof, substantially asand for the purpose specified.

4. The method of manufacturing filaments for incandescent lamps, whichconsists in crushing the twisted fiber of the filament, carbonizing thesame, and then subjecting the filament thus carbonized to the action ofan electric current while surrounded by hydrocarbon gas, the curvedportion or center of resistance of the filament being exposed longer tothe gas than the other portions of the filament.

In Witness whereof Ihereunto subscribe my name this 8th day of April, A.D. 1889.

ADOLF F. OPRERMANN.

\Vitnesses:

GEORGE P. BARTON, ELLA EDLER.

IOC

